1. Field of the Invention
This invention relates to flying or floating craft and to devices which utilize a flowing fluid or movement of a body in fluid to create a rotation and/or lift or thrust.
2. Description of the Prior Art
Helicopters were commonly provided with an autorotation arrangement. However the descending speed of the helicopter in auto-rotation is rather high. The "descent-speed slow down" maneuver is a delicate proceedure which often fails and the helicopters crash. The trend of development of helicopters is presently to reduce the weights. Also the weights of the rotors becomes reduced. That reduces as a side effect the time of the landing maneuver in auto-rotation and thereby increases the chance of failure of the landing maneuver, whereby the likeliness of a crash increases, when the engine of the helicopter fails.
In motor powered gliders is was custom in the former art to swing a motordriven propeller into and out of the craft, when a change over from motorless gliding to powered gliding and vice versa was desired. The swing out of the propeller resulted in a negative influence of the flight path of the glider. The sudden appearance and disappearance of the drag of the propeller brought a negative influence on the speed and stability of the glider in the surrounding air.